Color photographic material and processes for producing same



Patented May 24, 1949 COLOR PHOTOGRAPHIC MATERIALiAND PROCESSES .FORPRODUCING SAlglE Bela Gaspar, Hollywood, Calif., ass'ign'br to mum aChromogen Incorporated, a corporation'of Nevada.

APR 1'? 1951 No Drawing. Application May 29, 1944, Serial No.

537,967. =In GreatBritain August 28,- 1939' 19 Claims. (Cl. 95-6) i Thisapplication is a continuation in part of my application S. .N; 354,442;filed. August 27, 1940, now abandoned, and relates toimprovedphotographic light-sensitive:zmaterials in which at least @one of thelight sensitive. emulsions, used in the form of superposedlayers of amultilayer material; or in the form of difierently sensitized anddifierentl colored emulsion particles distributed within thesame layer,isz dyed with an azo dye and to improvements in or relating to-theprocess of producingzthe-samel The invention has for its purpose theprovision of improved material which can be produced in a very simpleand reliable; manner andin which the dye used for coloring. the.lightesensitive emulsion has onlya negligible tendency to: bleed :or

to difiuse during the manufacture, the storage or.

the processing of the. material.

It is already known touse water-insoluble dyes for coloringthe-light-sensitive emulsions or layers, the insoluble dyesbeingintroduced-assuchor produced Within the .colloid fromtheir components,by dye synthesis; or from their soluble. derivativesby decomposition. Itis obvious that.

the coloring of the colloid by means of a soluble dye is much simplerthan the incorporation of insolubleldyes', it only being necessar to addthe.

dye solution to. the colloidal. solution-or emulrsion. On the otherhand, itis a. Well-knownfactthat most of. the Water soluble azodyeshaveastrong tendency to diffuse and that owing to this property it becomesnecessary to precipitate the soluble dye within the colloid by aprecipitating agent. There are: only a restrictedunumbercor soluble dyesavailable which can be used without precipitating agent, such" as; forexample, the dyes referred to and used accordingtomy. prior BritishPatent Specification No. 445,806.;

According to the. present invention light-sensitive silver halideemulsions used in-the form of superposed layers in a multilayer materialor in the form of difi'erently sensitized and difierentlycoloredparticles aredyed by a: water oralkalisoluble polymeric azo dyederived from a diazotized aromatic amino compound. which is. capable ofcoupling with itself, the dye. molecule being formed by such couplingand containing a chain! wherein a plurality of: azo groups arepositioned-'- OH NH HO S $0 11 l in alternating? relationshipwithradicals of said aromatic. compound. It has been found that fromlow-molecular aromatic componentsgthere can be obtained by couplingof'the "dia'zotized aromatic amino compound withitself," dyes which haveahigh molecular-weight 'and 'wh-ich, 'on the one hand, are water-solublebutflon the other hand, have'only a negligibleten'clency to bleed ordiffuse. "Such dyesmay" readily be "employed inthelight-sensitive"silver halide emulsions or'in dyed filter layersadjacent to alight-sensitive silver halide emulsion layer. Layersdyedaccording to the invention"are-particularlyuseful for carrying outthe process =of producing dye images by local destruction of the ado-dyedescribed'for" examplain my prior United States Letters *Patent No;2,02051755dated November 1-2; 1935;

As examplespf suitable dyes of the kind de-' fined above there may .becited-the azo dye obtained by coupling"N-(p-aminobenzoyl )-II-acid withitselfor by coupling 1-amin0-4-sa1icoy1ami no-benzene-Z-sulphonic acidwith' itself. The process of producing dyes of' this kind may bedescribed by: way of an example as follows:

-Example 1'.--'N- (p-aminobenzoyl H-acid (so d'ium salt) dissolved inwater and *diazotized by acidifying. thersolutionnwith acetic acid andadding :sodium nitrite solution: 'The diazonium salt solution is: 'kept'atllow temperature for about an hour. Thereafter, sodium carbonate isadded to render the-solution alkaline-andthe solution is heated,thereafter, to about 50-60 C. A magenta dye is form-ed'which issaltedout b common salt. The dye maybe-represented by the followingformula-omitting any'termina1 groups which maybe present, whichdiscloses the charactor of the units going to make up the polymeric dyesubstance:

SIOaHT j it. a

in which the portion enclosed by the may be considered an azo dye unit.The letter 12 in both formulae represents an integer greater than oneindicating the chain characteristic wherein a p rality of azo groups arealternating with of the aromatic compound. If the high molecular weightpolymeric dye as shown in Formula B is reduced it can readily be seenhow it will break down to form a product of low molecular weight whichcan be represented OH NH and whose similarity to the units which went tomake up the polymeric dye, Formula A, is readily apparent.

For coloring emulsions the dye is dissolved in water and the solution isadded to the light-sensitive emulsion to diffusely distribute the dyethroughout the light-sensitive emulsion. For

s -xed 1 producing filter layers the dye solutmn 1 m1 dye units, andevery single dye unit itself may with a gelatin solution which is coatedto form a filter layer on a light-sensitive layer. For coloringlight-sensitive emulsions about 1-2 grams of the dye are used per sq. m.emulsion layer to obtain a diffusely dyed layer. layers in which one ormore layers are dyed by means of the dyes defined above may be coated insuperposition on a common support.

Example 2.--5 p amino benzoylamino) phenol-2-sulphonic-a'cid isdiazotized in known 3 manner and to the diazo solution is added 4%ammonia solution and 5% pyridine. After coupling, the solution isacidified with dilute hydrochloric acid, and the resulting yellow dye issalted out and filtered. The dye has a good solubility and shows nodiffusion in gelatine. About 0.3 to 1.0 g. dye can be used per squaremeter coating.

The azo dyes disclosed in the above description are large moleculescontaining several azodye units; these azo-dye units alternating withheteronuclear bonds which link said azo-dye units together. Thefollowing general formula, omitting any terminal groups which may bepresent, represents the character of the dyes:

Where Arr and Arz stand for aromatic heterocyclic, or aliphaticradicals, capable of carrying azo groups, N=N stands for an azo linkage,and B for a heteronuclear bond connecting two dye units,

and where n represents an integer greater than one. The letter a meansone, in the case of the dyes disclosed above. However, I have found thatother values for a are also possible, as will be described in greaterdetail. Theexpression heter onuclear bond means a chemical linkageinterrupting the system of conjugation, and, therefore, practicallyexcluding any essential influence of a dye unit (or groups within such adye unit) on the color characteristics of any one of the other azo-dyeunits beyond the bridge B. The

expression azo-dye unit means that part of the molecule limited by twoheteronuclear bonds (or by one bond if it is a terminal group) and whichdetermines the spectral qualities of the dye. If

Differently colored l 4 a dye of the indicated formula (where a equalsone) is reduced, a product of the formula is formed. The size of thisreduction product depends only on the size of the single components andis independent of the value for n in the original dye. The reductionproduct of a non-diffusing high molecular dye of the indicated formulais, therefore, easily removable from a photographic colloid by washing.

It has been found the polymeric dyes prepared in other ways thandescribed above have the same advantages and serve as well forcoloration of photographic colloids; particularly silver halideemulsions containing gelatine, or other watersoluble or water-permeablecolloids, such as methyl cellulose or cellulose glycolic acid, polymericvinyl derivatives, and other colloids used for multilayer colorphotographic materials whereby in each differently sensitized silverhalide layer a differently colored dye is incorporated.

The dyes, according to the invention, are represented by the samegeneral formula given above; the new dyes may contain identical orunidentical contain one or more azo groups. The number of units, n, isdetermined or undetermined. In order to clarify the objects of theinvention, a detailed description and further defiinitions are given asfollows:

1. The dye unit Any low molecular weight azo dye which is capable ofbeing linked to other (identical or unidentical) azo dyes by aheteronuclear bond is a dye unit according to the definition of thepresent specification. This azo-dye unit can be a monoazo dye or a truedisazo, trisazo, or polyazo dye.

, The expression true polyazo dye means a polyazo dye, the azo groups ofwhich are linked together by a conjugated system, and which, therefore,influence the chemical and optical qualities of each other. The letter ain the general formula given above indicates the number of azo groupsWithin one azo-dye unit. In the case of a monoazo dye a is one. If theazo dye unit is a true disazo dye a becomes two, and in a trisazo dye 0.assumes the value of three. A polymeric polyazo dye (a 1 and n 1 in thegeneral formula) upon reduction gives n.(a-1) molecules of the formula,

. and n-1 molecules of the formula exclusive of the terminal moleculesall of which are easily removable from the photographic colloid,independently of the polymeric grade n of the original dye.

2. The combination of dye units The dye units, linked together by aheteronu clear bond are, in the simplest case, identical. However, theymay be different as well. These different dye units linked together canbe of identical or different coloration; one azo-dye unit may be amonoazo dye and the next azo-dye unit may be a polyazo dye. It is,therefore, possible to combine different yellow, magenta, or blue-greenazodye units to form yellow, magenta, red, cyan, violet, green or blackdyes.

3. The heteronuclear bond The dye units contained in the polymeric dyeare bound by a carbon to carbon linkage or by any bridge formed bysubstituted carbon atoms or hetero-atoms, such as, for example, -ArO, O,S-, -SO2-, --CO-, NH-CO-, alkylene, arylene, Oalkylene--O, O-arylene,NE, -NHCONH, ArCOi-, SO2NI-I, -1 TH-XNH, and NH-YNI-I wherein X is thedivalent radical of a dibasic organic acid and Y is a bivalenthydrocarbon residue. Any radical is suitable provided that it interruptsthe conjugation of the chain, and that it does not increase themolecular Weight or decrease the solubility of the resulting reductionproject to such an extent that it will prevent the removal ordissolution of the product from the photographic layer.

Substituents within the dye units The dye units may contain one or moresolubili zing groups such as, for example, sulphonic or carboxylic acidgroups which make them water soluble either in the free acid form or inthe form of salts; or they mi ht contain groups which facilitate theirsolubility in organic solvents, or both in water and organic solvents,or in a mixture of water and organic solvents. Such groups arehydroxyalkyl groups, polyhydroxyalkyl groups, hydroXy-amino-alkyl,quaternary amino groups, and many other substituents. According to theinvention the solubility properties of the dyes are selected only withrespect to the most suitable solvent for a chosen photographic colloidsince they have, in spite of their great solubility, no tendency towarddifiusion, and, furthermore,

after reduction they form low molecular weight reduction products whichcan be easily removed from a photographic colloid by washing, or whichgo into solution already during the reduction of the polymeric azo dye.Up to new it has been considered necessary to use dyes which containedonly a minimum number of solubilizing groups; or to 5. The polymericgrade it It depends on the methods of synthesis chosen if the polymericgrade 11. is determined or undetermined.

The coupling of a polydiazo compound with a coupling compound having twoor more coupling positions yields a polymeric azo dye where n is largebut not determined. Another method to synthesize polymeric dyes of largebut undetermined molecular size consists in connecting monoazo, disazo,trisazo, or polyazo dyes, which have reactive groups in the terminalgroups, with a bivalent reagent to link the single dyes into a polymericazo dye of a larger molecule.

The synthesis of dyes having a determined molecular size can beperformed, i. e., by coupling a diazo or tetrazo compound with acoupling compound which contains an amino group capable of furtherdiazotation and by diazotizing the resulting amino-azo dye and couplingwith an equal or similar coupling compound. This 0 1-- eration isrepeated as often as necessary to obtain a polymeric azo dye ofsufficiently large molecular weight. After each operation a diffusiontest is made and a non-difiusing dye results after reaching a suitablesize of molecule. The number of dye units required to reach a dye stableto diffusion varies with the chemical properties of the couplingcompound and also with the properties of the photographic colloids used,and can be easily determined by simple diffusion tests for each dye. Thediffusion test may be carried out, for example, in the following manner,i. e., a quantity of colorless to 10 per cent gelatine or otherphotographic colloid solution is coated on a base such as celluloid filmor glass plate and dried. A second coating is placed on top of thisclear coating, using the same concentration of colloid to which asolution of the dye has been I added in suflicient quantity to reach thedesired dye density. After drying, the material is soaked in water, andthe upper layer is removed with a sharp instrument, and the lower clearlayer examined for evidence of difiusion. In most cases the material iscarried through a sequence of photographic processing baths such as thedeveloper, fixing bath, dye bleach, etc., and after final washing thedyed layer is removed and the lower clear layer examined for evidence ofdiffusion.

The polymeric gradev 71. required to render the dye stable towardsdiffusion is inversely proportional to the number a of azo groups withinone azo-dye unit. I have found that the product dxn must be greater thantwo in order to prevent diffusion of the dyes in the processing baths.However, a higher polymeric degree than the minimum degree is preferableand does not adversely affect the solubility and tinctorial power of thedye nor the molecular size of the reduction products of the dye.

The above mentioned general methods are illustrated by the followingspecific examples. There are, of course, many forms of the inventionother than described in these specific examples.

Example 3.9.3 grams of aniline are diazotized and coupled in knownmanner with 22 grams of 1- [4-amino-pheny1l -5--pyrazolone 3 carbonic(Beilstein, Handbuch der Organischen Chemie, 4th ed., supplementary vol.XXV, page 568) in sodium carbonate solution. After completion of thecoupling the resulting dye is salted out,

filtered off, washed and dissolved in water. 6.9 grams of sodium nitriteare added to the dye solution which is then poured into ml. ofhydrochloric acid (D=1.19) diluted with ice water. After stirring at atemperature below 6 C. for 1 hour the resulting diazo compound isstirred into a solution of 22 grams of sodium carbonate and quantity of1- [4-amino-pheny1] -5-pyrazolone-3- carbonic acid, as described above,and the resulting dye is precipitated with dilute hydrochloric acid. Thedye, when tested for diffusion, shows with most gelatines only a slightdiffusion. When two further diazotizations and couplings are performedthe same way as described above no diifusio'n occurs with the resultingdye. The dye is believed to have the following formula:

where m stands for either two or four.

In the above example the aniline can be re- 10 I SOaH S H filtered off,and dissolved in a sodium carbonate solution. Phosgene gas is introducedunder cooling and stirring, whereby a polymeric azo dye is formed inwhich the dye units coon o on{ are linked by NH-CO-NH- groups.

The same dye is obtained by tetrazotizing 24.2 grams ofdiamino-diphenylurea and coupling the same in a 20% pyridine solutionwith 26.8 grams of carbonyl-bis-l- (l-amino-phenyl)-5-pyrazolone-3-carbonic acid.

Example 5.-Instead of reacting the monoazo dye described in theforegoing example with phosgene, other acid chlorides derived frompolyvalent acids, such as succinyl chloride, can be used: 33.9 grams ofthe monoazo dye described in Example 4 are dissolved in anhydrouspyridine, and 15.5 grams of succinyl chloride are stirred in smallportions into the cooled solution. Half an hour after the addition ofthe chloride is completed, the temperature is raised to 50 C. and keptat this temperature for 1 hour. The dye is finally precipitated byadding, under cooling, dilute hydrochloric acid. After filtering off thedye is dissolved in sodium carbonate solution and purified byreprecipitation with acid. A polymeric yellow azo dye results in whichthe monoazo dye units are linked together with groups. A furthervariation consists in treating the monoazo dye of the Example 4 with18.8 grams of ethylene bromide at 90 C. under reflux in dioxane in thepresence of calcium car- SOaH H0 8 bonate. Hereby a polymeric azo dye isobtained, the monoazo dye units of which are connected by C(OH) anethylene bridge.

Example 6.-34.4 grams of benzidine-2,2-disulphonic acid are tetrazotizedand coupled with 53.4 grams of 1.1-[2.2-disulpho-diphenylene- (4,4)l-bis-(5-pyrazolone-3-carbonic acid) (Bellstein, l. c.) in a coldaqueous solution of 10% pyridine. The yellow dye is precipitated withdilut hydrochloric acid solution, filtered off, and washed with alcohol.The dye, neutralized with 16.4 grams of sodium carbonate, forms a yellowsolution in water which is ready for addition to a photographic colloid.For color photographic or filter purposes 0.3 to 1 gram of the dye isused per square meter. The photographic layers dyed with this dye areentirely free of diffusion. The probable structure of the dy is C O OH OO OH O (OH{ \C S 0 H S 0 11 7b The isomer dye having the sulphonic acidgroups attached in the 3,3'-position (instead of the 2,2- position) ofthe diphenylene radicals has a similar shade.

Example 7 .a. 34.4 grams of benzidine-2.2- disulphonic acid aretetrazotized in dilute hydrochloric acid solution in known manner. Tothis tetrazo solution, a solution containing 31.9 grams of H-acid, 8.3grams of sodium acetate and 6 ml. of acetic acid is added slowly whilestirring. The temperature is kept at 5 C. for 2 hours. A bluishredmonoazo dye forms. Thereafter about ml. of pyridine are added wherebythe bluish-red monoazo dye transforms into a blue-green polymeric dye.After 1 hour the solution is acidified with an excess of hydrochloricacid, and the polymeric blue-green azo dye precipitates in amor phousform. The liquid is decanted and the precipitate washed with 5% sodiumchloride solution. For purification, the dye is dissolved in aqueoussodium carbonate solution, salted out, filtered and washed with 5%sodium chloride solution.

b. A dye similar to that described in Example 7a is obtained by thefollowing procedure: 34.4 grams of benzidine-2,2'-disulphonic acid aretetrazotized in hydrochloric acid solution. To this tetraazo solution, asolution containing 63.8 grams of H-acid, 16.6 grams of sodium acetate,and 12 ml. of acetic acid is added in the same Way as in Example 7a.After standing for two hours, to this solution which contains a magentadisazo dye, a tetraazo solution prepared with 34.4 grams ofbenzidine-disulphonic acid and ml. of pyridine is added whereby ablue-green dye is formed which is isolated and purified as in Example7a.

The probable formula of the dye formed in Example a is 0H NHl "l N=N N=NI SO|H H0 8 SOgH HO S SOQH l and the probable formula -:of the dyeformed in aniline 2 sulfonic acid with -1-amino-n'aph- Example bis:thalene-Y-sulfohic acid, 'diazotizing the resulting on 'NH; 111m on Thedyes are well soluble in water and their monoazo dye and coupling itwith 1-amino-2- gelatine coatings are free of difiusion intoadjamethoxynaphthalene-G-sulphonic acid. This cent gelatine layers. dyeis then diazotized and coupled in pyridine and Instead of thetetrazotized benzidine -2,2-diammonia with 2-amino-5-naphthol-7-sulfonicsulphonic acid in the foregoing examples, a acid. The making of similartrisazo dyes is denumber of other tetrazo compounds may be used 5scribed in the U. S. Patent No. 1,602,991. The rewith equal success,such as for example: tetrazsulting trisazo dye is dissolved, and theoxalyl otized diaminodi-phenylsulphone, diaminodigroup is split off withcold 5% sodium hydroxide phenylsulphone-sulfonic acid,diaminodiphenylsolution. Thereafter, the dye is salted out,filsulphone-disulphonic acid, dianisidine, diaminotered off, dissolvedin a sodium carbonate pyridine .diphenylmethane, dialninodibenzyl,diaminoa solution and treated with phosgene gas. A bluebenzophenone,diaminodiphenyl-sulpl'lide, or digreen polymeric azo dye is formed whichis supaminodiphenyl ether. The aforementioned posed to have the formula:

soau S0311 compounds might contain further substituents For colorphotographic purposes 0.5 to 1 gram such as alkoxy, alkyl, oxyalkylgroups or halogens. of the dye can be used in silver halide emulsionsExample 8.-33.1 grams of 3,3'-diamino-4,4='- per square meter.dimethoxy-diphenylmethane chlorohydrate are What is claimed is:tetrazotized in known manner and coupled in l. A photographic materialcomprising at least 5% Pyridine solution with 107.6 grams of twosuperposed colloid layers, at least one of the p-amino-benzoyl-H-acid.The diamino disazo layers being a light sensitive silver halide emulsiondye is precipitated with hydrochloric acid and solayer and at least onelayer comprising a high dium chloride, filtered off, dissolved in waterand molecular weight dye which is soluble in a subtetrazotized in acidsolution with 13.8 grams of 40 stance selected from the group consistingof sodium nitrite and coupled with 107.6 grams of Water and aqueousalkali and which includes the p-aminobenzyl-H-acid. The diamino tetrazofollowing general structure dye is isolated in the same way as describedfor Ar the diamino disazo dye. The diamino tetrazo dye 5 n istetrazotized and coupled again, following the f rm y a pl r lity of idenical low molecular identical procedure. It is advisable to purify thewei ht members ArN1=N, wherein Ar stands dyes in each step by dissolvingand reprecipitatfor a gro p Which as t a Co p n P i o ing them. Thefinal product isamagenta hexazo and at le st ne s lt-formin sub ituentand dye which is believed to hav the following comprises an aromaticradical capable of carryformula: 59 ing an azo group, n stands for aninteger greater The dye has a. good solubility in water and is than one,said members Ar-N='N being linked added to a gelatine silver bromideemulsion in a together by the azo group of one member being quantity of0.5 to 1 gram per square meter. It attached to the coupling position ofthe next does not diffuse into adjacent 'gelatine layers. member.

In the above example in place of 3,3-diamino- 2. A photographic materialcomprising two 4,4-dimethoxy-diphenylmethane many other disuperposedcolloid layers, at least one of the amino aryl compounds such asp-diaminodi-phenyl layers being a light sensitive silver halideemulether, 2,2'-dichlorobenzidine, or diamino-dision layer comprising ahigh molecular weight phenylurea can be used. The p-aminobenzoyL dyewhich is soluble in a substance selected from H-acid can be substitutedin one, two, or all the group consisting of water and aqueous alcoupling steps with aminoanisolsulfo-H-acid or kali and which includesthe following general aminobenzoyl-K-acid. Furthermore, the laststructure coupling can be made with a coupling compound,

which is free of diazotizable amino groups, such asp-toluenesulfo-H-acid or dichlorobenzyl-K- formed by a plurality ofidentical low molecular acid. weight members Ar-N=N, wherein Ar standsExample 9.A trisazo dye is made in known for a group which has both acoupling position manner by coupling, diazotized 4-oxalylam'i-noand atleast one salt-forming substituent and ll comprises an aromatic radicalcapable of carrying an azo group, n stands for an integer greater thanone, said members ArN=N being linked together by the azo group of onemember being attached to the coupling position of the next member.

3. A photographic material comprising a lightsensitive silver halideemulsion and a high molecular weight dye in the presence of said silverhalide which dye is soluble in a substance selected from the group ofsubstances consisting of water and aqueous alkali and includes thefollowing general structure formed by a plurality of identical lowmolecular weight members ArN=N, wherein Ar stands for a group which hasboth a coupling position and at least one salt-forming substituent andcomprises an aromatic radical capable of carrying an azo group, n standsfor an integer greater than one, said members ArN=N being linkedtogether by the azo group of one member being attached to the couplingposition of the next member.

4. A photographic material having a layer comprising a light-sensitivesilver halide emulsion and a high molecular weight dye which is solublein a substance selected from the group of substances consisting of waterand aqueous alkali and which includes the following general structureformed by a plurality of identical low molecular weight members ArN=N,wherein Ar stands for a group which has both a coupling position and atleast one salt-forming substituent and comprises an aromatic radicalcapable of carrying an azo group, n stands for an integer greater thanone, said members ArN N being linked together by the azo group of onemember being attached to the coupling position of the next member.

5. A process for producing a colored photographic material comprising atleast two superposed colloid layers, at least one of said layers being alight sensitive silver halide layer and at least one of said layersbeing a colored colloid layer, which comprises coloring the colloid usedfor the production of said colored colloid layer with a soluble highmolecular weight dye which includes the following general structureformed by a plurality of identical low molecular weight members ArN=N,wherein Ar stands for a group which has both a coupling position and atleast one salt-forming substituent and comprises an aromatic radicalcapable of carrying an azo group, 7:, stands for an integer greater thanone, said members ArN=N being linked together by the azo group of onemember being attached to the coupling position of the next member.

6. A process for producing a colored photographic material comprising atleast two superposed colloid layers, one of said layers being a coloredlight-sensitive silver halide emulsion layer, which comprises coloringthe colloid used for the production of said colored light-sensitivesilver halide emulsion layer with a soluble high molecular weight dyewhich includes the following general structure formed by a plurality ofidentical low molecular weight members ArN=N, wherein Ar stands for agroup which has both a coupling position and at least one salt-formingsubstituent and comprises an aromatic radical capable of carrying an azogroup, n stands for an integer greater than one, said members ArN=Nbeing linked together by the azo group of one member being attached tothe coupling position of the next member.

7. A process for producing a colored photographic image in aphotographic material comprising a plurality of colloid layers, at leastone of said layers containing a silver image and at least one of saidlayers being diffusely dyed with a soluble high molecular weight dyewhich includes the following general structure formed by a plurality ofidentical low molecular weight members ArN=N, wherein Ar stands for agroup which has both a coupling position and at least one salt-formingsubstituent and comprises an aromatic radical capable of carrying an azogroup, n stands for an integer greater than one, said members ArN=Nbeing linked together by the azo group of one member being attached tothe coupling position of the next member which comprises treating saidmatorial to locally destroy by reduction said dye in the presence ofsaid silver image and washing said material.

8. A process for producing a colored image in a colored photographiccolloid layer containing a silver image, said layer being difiusely dyedwith a soluble high molecular weight dye which includes the followinggeneral structure formed by a plurality of identical low molecularweight members ArN=N, wherein Ar stands for a group which has both acoupling position and at least one salt-forming substituent andcomprises an aromatic radical capable of carrying an azo group, itstands for an integer greater than one, said members ArN=N being linkedtogether by the azo group of one member being attached to the couplingposition of the next member which comprises treating said material tolocally destroy by reduction said dye in the presence of said silverimage and washing said material.

9. A process for producing a colored image in a colored photographiccolloid layer containing a silver image, said layer being difiusely dyedwith a soluble high molecular weight dye which includes the followinggeneral structure:

formed by a plurality of identical low molecular weight members ArN=N,wherein Ar stands for a group which has both a coupling position and atleast one salt forming substituent and comprises an aromatic radicalcapable of carrying an azo group, n stands for an integer greater thanone, said members ArN=N being linked together by the azo group of onemember being attached to the coupling position of the next member, whichcomprises treating said material to locally destroy by reduction saiddye in the presence of said silver image and removing the dye reductionproducts from said layer by washing.

10. A photographic material comprising at least two superposed colloidlayers, at least one of the layers being a light sensitive silver halideemulan -m9 sion layer and at least one layer comprising a soluble highmolecular weight dye which carries at least one solubilizing group andincludes the following general structure:

formed by a plurality of low molecular weight -members wherein An and AHstand for a group comprising a radical selected from the classconsisting of aromatic, heterocyclic and aliphatic radicals, B standsfor a heteronuclear bond, it stands for an integer greater than one anda stands for an integer from one to four and the product of a and n isgreater than two.

11. A photographic material comprising at least two. superposed colloidlayers, at least one of the layers being a light sensitive silver halideemulsion layer and at least one layer comprisinga soluble high molecularweight dye which carries atv least one solubilizing group and includesthe following general structure:

iormed by a plurality of low molecular weight members wherein An and Anstand for a group comprising a radical selected from the classconsisting of aromatic, heterocyclic and aliphatic radicals capable ofcarrying an azo group, B stands for a heteronuclear' bond, n stands foran integer greater than one and a stands for an integer from one to fourand the product of a and n. is greater than two.

12. A photographic material comprising at least two superposed colloidlayers, at least one of the layers being a light sensitive silver halideemulsion layer and at least one layer comprising a soluble highmolecular weight dye which carries at least one solubilizing group andincludes the following general structure:

formed by a plurality of identical low molecular weight members whereinAIl and Are stand for a group comprising a radical selected from theclass consisting of aromatic, heterocyclic and aliphatic radicals, B

[B( AI1N=N a Al2] n formed by a plurality of difierently colored lowmolecular weight members B(A11N=N)a Arawherein An and Alz stand for agroup comprising a radical selected from the class consisting ofaromatic, heterocyclic and aliphatic radicals, B stands for aheteronuclear bond, 11, stands for an integer greater than one and 0,stands for an intei4 gerfrom one to four and the product of a andgreater than two.

14. A photographic material comprising at least two superposed colloidlayers, atleast one. of the layers being a light sensitive silver halideemul;- sion layer and at least one layer comprising a soluble highmolecular weight dye which. carries at least one solubilizing group andincludes the following general structure:

formed by a plurality of identical' low molecular weight members whereinAIl andArz stand for a group comprising a. radical selected. from theclass consisting, of aromatic, heterocyclic and aliphatic radicalscapable of carrying an azo group, B stands. for a heteronuclear bond, nstands for an integer greater. than one and it stands for an integerfrom one to four and the product of c and n is greater than two.

1.5. A photographic material comprising at least two: superposed colloidlayers, at least. one of the layers being a light sensitive silverhalide emulsion layer and at least one layer comprisin a soluble highmolecular weight dye which carries at leastone solubilizinggroup. andincludes the tollowing general structure:

formed by a plurality of differently colored low molecular weightmembers wherein An and An stand for a group comprising a radicalselected from the class consisting of aromatic, heterocyclic and.aliphatic radicals capable of carrying an azo group, B stands for aheteronuclear bond, 11 stands for an integer greater than one and astands for an integer from one to four and the product of a and n isgreater than two.

16. A photographic material comprising at least two superposed colloidlayers, at least one of the layers being a light sensitive silver halideemulsion layer and at least one layer comprising a soluble highmolecular weight azo dye formed by a chain which contains at least fourlow molecular Weight members, each carrying at least one azo group andat least one heteronuclear bond linking together said members, thenumber of said heteronuclear bonds multiplied by the number of azogroups conjugated with each other giving a product which is greater thantwo.

1'7. A photographic material comprising at least two superposed colloidlayers, at least one of the layers being a light sensitive silver halideemulsion layer and at least one layer comprising a soluble highmolecular weight dye which carries at least one solubilizing group andincludes the following general structure:

[B( Ar1N=N-) aA1'2-]n formed by a plurality of low molecular Weightmembers B(Ar1-N=N--)aAr2 wherein An and Arz stand for a group comprisinga radical selected from the class consisting of aromatic, heterocyclicand aliphatic radicals capable of carrying an azo group, B stands for aheteronuclear bond which in at least one low molecular weight member ofthe series comprises the group -CONI-I-, it stands for an integergreater than one and a stands for an integer formed by a plurality oflow molecular weight members B(Ar1N=N)Ar2 wherein An and A132 stand fora group comprising a radical selected from the class consisting ofaromatic, neterocyclic and aliphatic radicals capable of carrying an azogroup, B stands for a heteronuolear bond which in at least one lowmolecular weight member of the series comprises the group SO2NH, nstands for an integer greater than one and a stands for an integer fromone to four and the product of a and n is greater than two.

19. A photographic material comprising at least two superposed colloidlayers, at least one of the layers being a light sensitive silver halideemulsion layer and at least one layer comprising a soluble highmolecular weight dye which carries at least one solubilizing group andincludes the following general structure:

[B(Al'1-N N-)aAY2-]n formed by a plurality of low molecular weightmembers B(--AI1N=N)aAI2-- wherein An and Are stand for a groupcomprising a radical selected from the class consisting of aromatic,heterocyclic and aliphatic radicals capable of carrying an azo group, Bstands for a heteronuclear bond which in at least one low molecularWeight member of the series comprises the group -NI-IXNH wherein X isthe divalent radical of a dibasic organic acid, n stands for an integergreater than one and 0. stands for an integer from one to four and theproduct of a and n is greater than two.

BELA GASPAR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,071,688 Gaspar Feb. 23, 19372,178,167 Gaspar Oct. 31, 1939 2,281,149 Gaspar Apr. 28, 1942 2,286,714Chechak June 16, 1942 2,286,837 Seymour June 16, 1942 2,294,892 Carrollet al Sept. 8, 1942 2,294,893 Carroll et a1. Sept. 8, 1942 2,342,620Woodward Feb. 22, 1944 2,346,531 Allen et a1 Apr. 11, 1944 FOREIGNPATENTS Number Country Date 219,653 Great Britain Apr. 30, 1925 822,348France Dec. 28, 1937 496,559 Great Britain Nov. 30, 1938 204,534Switzerland Aug. 1, 1939 541,073 Great Britain Nov. 12, 1941 549,176Great Britain Nov. 10, 1942 551,500 Great Britain Feb. 25, 1943 551,501Great Britain Feb. 25, 1943

